Power transmission belts are widely used throughout the industry, and the manufacture and sale of such belts is very competitive. One common technique used to make such belts is to ply up layers of belt materials on a cylindrical drum and form a belt sleeve, and cut individual belts from the sleeve. One example of such a belt sleeve is shown in U.S. Pat. No. 3,031,364. Typically, such a belt sleeve is formed of various plies of material used to form the body of the belt. The body is composed of various arrangements and layers of materials, such as fabric layers, cushion layers and fiber loaded layers.
A load carrying section may also be provided, which includes a helically wound load carrying cord spiraled on the drum in a specified position during the building process. Such belts, having load carrying sections are shown in U.S. Pat. Nos. 2,773,540, 3,987,684, 4,264,315, 4,296,640 and 4,734,086. The resulting belt sleeves may be cured first as a sleeve and then cut, or they may be left uncured, with each sleeve then being cut into belt elements. The belt elements may then be wrapped by a fabric sheet prior to curing as shown in U.S. Pat. No. 4,096,764.
The above method of making a belt sleeve is both labor intensive and time consuming. Inventories of various ply stocks in various widths and thicknesses have to be maintained. Also, precise placement and spacing of the spiralled load bearing cord between the overcord or tension section, and undercord or compression section using the above method is sometimes difficult to maintain.
Conveyer belt sleeves have been made by winding rather narrow fiber bats around rollers to form layers which, after needling, are then cut into belt elements as shown in U.S. Pat. No. 3,673,024. However, the conveyer belt sleeve formed does not have a separate load carrying section such as a spiralled cord; consequently, belts made from such sleeves have minimum tensile load carrying capability.
Load bearing cord is used in the power transmission belt of U.S. Pat. No. 4,123,946, but it is necessary to first embed the cord in an elongated strip of polymeric material. This is done by extruding the substantially uncured polymeric material and load carrying cord simultaneously through an extrusion orifice and forming a strip, and then, winding this strip onto a cylindrical drum. Thus, an elongated strip is formed having the load carrying cord extending through and embedded throughout its entire length. However, the wrapping of such strips of polymeric material containing load carrying cord in an adjoining relationship about the drum as shown in the patent is a relatively slow process limited by the extruder output and the wrapping is not easy to achieve because the strip must be bent and helically wound along its narrow edge causing the strip to widen at the edge and neckdown at the opposite edge. It is also difficult to precisely position the load carrying cord relative to the surfaces of the finished belt particularly when the strip changes width dimensions during winding. This is a critical factor affecting the final physical characteristics of the finished belt in terms of locating the load bearing cord in a constant equatorial plane.
It is an object of this invention to provide a power transmission belt formed of belt material and a load carrying cord where the belt material is in the form of a continuous narrow strip instead of layered wide sheets or plies. The strip eliminates the need for an inventory of wide stock sheets and the processing equipment to make the inventory. The continuous strip of belt material is easily helically wound about a belt building drum with an adjacent cord to form a belt sleeve. This decreases the building time required for each belt and results in cost savings.
It is another object of this invention to precisely place the load carrying cord. This is achieved during helical winding by adhering the load carrying cord to an adjacent surface of the strip of belt material and winding the cord and the strip of belt material simultaneously about the building drum. Thus, the belt material with the adhered cord helps achieve uniform cord spacing. The adjacent belt material between successive cords acts as a uniform insulation that retards the development of cord line sheer and substantially prevents self abrasion between successive cords during the belt operation.
It is another object of the instant invention to wrap the strip or strips of belt material simultaneously with the load bearing cord or cords so that inclined plies of belt material are formed with cord between each ply for easy helical winding around a building drum.
It is a further object of the invention to form a belt sleeve on the belt building drum by simultaneously winding belt material with the load bearing cord. The so formed belt sleeve is then cut into individual belt elements and covered with a fabric wrap. The covered belt elements are then cured to define a finished belt. Alternatively the belt sleeve may be cured first and then cut, ground, or otherwise severed into the desired belt shape such as a cut edge V-belt or V-ribbed belt.
Other detailed features, objects, uses and advantages of this invention will become apparent in the embodiments thereof presented in the following specifications, claims and drawings.